Since 1960 decade, the Petrochemical industry of Taiwan has been growing along with the construction quantity of Petrochemical industry, and the development of Petrochemical industry has been also gradually improved. Broadly speaking, the Petrochemical industry regards a final product processed from Petrochemical raw materials manufactured by oil or nature gas.
The relative field of the Petrochemical industry includes: Basic chemical materials manufacturing; Petrochemicals Manufacturing; Fertilizers Manufacturing; Synthetic Resin, Plastic Materials Manufacturing; Synthetic rubber and Man-made Fibers Manufacturing. Petrochemicals can include Ethylene, Propylene, Butadiene, benzene, toluene and Xylene, etc. The aforesaid raw materials can be transformed to intermedia materials via processes such as high-temperature and high-pressure Pyrolysis, and a verity of plastics, rubber, Synthetic Fibers and chemicals can be achieved by chemical processes including polymerization, esterification or alkylation, and a final product can be achieved by processing aforesaid polymaterials via specific processes. Therefore, Petrochemical products are everywhere in daily life so as to be inseparable with the modern livelihood needs.
Although Petrochemical products bring convenience for our life, the synthetic polymer materials so called synthetic plastic such as Polypropylene, Polyethylene, PVC and Polystyrene have extremely high chemical stability, high acid and alkali-resistance and are free of mold and erosion. The synthetic plastic is the main ingredient of city solid waste and is even called white population. To slow down the environmental damage resulted from synthetic plastic, partial nations have published relative acts to restrict the usage of traditional plastic bags and promoted people to use own green bags. In addition to lowering the usage of traditional plastic bags, each country also put into the development of the alternative materials of traditional plastic bags or replace the traditional plastic bags with Biodegradable Plastic (BDP).
Biodegradable Plastic, or called biodegradable plastic well known by people can be also called green plastic. In a natural landfill or composting environment, a green plastic can be metabolized and decomposed by microorganisms to generate water, Carbon dioxide or Methane, therefore the green plastic is a plastic material capable of being degraded in natural and is less harmful to the environment. Among various plastic materials capable of decomposed in biological, the BDP is considered to be one having more prospect because of capable of being completely degraded in biological, wherein Polyhydroxyalkanoate (PHAs) can be further applied to Biomedical materials, Tissue engineering materials, Electrical materials and Packaging materials because of including features of biodegradable and biocompatibility.
The thermoplastic of PHAs is similar to that of the Petrochemical plastic (Lee, 2012). PHAs are intracellular polyesters intracellularly synthesized by various sorts of bacterial. Currently, most of the relative researches of PHAs are performing pure culture by using species capable of accumulating PHAs to investigate a best condition for producing PHAs. By using pure culture, PHAs can be produced more, however, the operation cost may correspondingly raise when PHAs is produced under the best condition. In another aspect, the sewage treatment proportion have been much raised corresponding to the rapidly growing quantities of sewage treatment plant. Further, outsourcing treatment is urgently needed by lots of waste sludge produced every year. The cost of treating waste sludge has been raised day by day so as to occupy 60% of the total cost of a sewage treatment plant (Wei et al, 2003), and the sewage treatment industries are difficult to deal with the problem.
Concluding theparts to be improved of current technology and the problems to be solved in the industry, the present invention provides a concept that producing PHAs by reusing waste sludge, at the same time the objects including lowering the cost of producing PHAs, simplifying the produce of PHAs, speeding the productivity of PHAs and treating excess waste sludge can be achieved, therefore promoting the industrial utilization of PHAs.